Expression Class Reference

Represents base class of all expressions. More...

#include <expression.h>

Inheritance diagram for Expression:

Collaboration diagram for Expression:

List of all members.

Public Member Functions

Expression (EXP_TYPE _type)

Constructor.

virtual ~Expression ()

virtual void scopeCheck (vector< unsigned > &def_vars, vector< unsigned > &introduced_vars, vector< unsigned > &violating_vars)

Returns if all used variables were previously (through a for-clause) defined or if a variable leaves their defined scope.

virtual void replaceVarId (unsigned old_id, unsigned new_id)

Replaces all matching variable IDs by a new one.

virtual void mergeSequences ()

Merges belonging together XQuery sequences into a single sequence.

virtual void extractFSAMap (FSAMap *fsamap, unsigned parent_var)

Extracts the needed first straight ancestor (FSA) variables map.

virtual void extractParVarMap (ParVarMap *parvarmap)

Extracts the needed parent variable (ParVar) map.

virtual void extractDependencies (vector< DependencySet * > *depset)

Extracts the needed dependencies of a query.

virtual Expression * placeSignOffs (vector< SignOffExpression * > &signoffs)

Places all signOff-statements in the corresponding query.

virtual void rewriteWhereExps ()

Rewrites all where-clauses in the query into equivalent if-expressions.

virtual void rewriteEmptyFuncts ()

Rewrites all fn:empty XQuery functions into equivalent fn:not(fn:exists) XQuery functions.

virtual void rewriteVarstepCondExps ()

Rewrites all if($x) if-conditions into equivalent if(fn:not(fn:empty($x))) XQuery expressions.

virtual void rewriteAggregateFuncts ()

Rewrites all arguments of all aggregate functions into an equivalent for-clause (with return-clause).

virtual void rewriteVarsteps ()

Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause).

virtual void print (OutputStream &dos) const =0

Prints the expression.

virtual void init (BufferNode *root)

Initializes the query for evaluation.

virtual void eval (OutputStream &eos, Environment *env, unsigned modus)

Evaluates the expression in the given environment.

const EXP_TYPE getType ()

Returns the EXP_TYPE of the corresponding expression.

void setType (EXP_TYPE _type)

Sets the EXP_TYPE of the corresponding expression.

virtual bool containsDirectOutput ()

Returns if the corresponding expression produces direct output.

Protected Attributes

TagMap * tagmap

EXP_TYPE type

The entered EXP_TYPE.

Detailed Description

Represents base class of all expressions.

Author:: Michael Schmidt
Gunnar Jehl

Version:: 2.1

License:: Software License Agreement (BSD License)

Definition at line 92 of file expression.h.

Constructor & Destructor Documentation

Expression::Expression ( EXP_TYPE _type )

Constructor.

Constructor - creating object for an EXP_TYPE.

Parameters:

[in] _type EXP_TYPE.

Definition at line 37 of file expression.cpp.

Expression::~Expression ( ) [virtual]

Destructor.

Definition at line 41 of file expression.cpp.

Member Function Documentation

bool Expression::containsDirectOutput ( ) [virtual]

Returns if the corresponding expression produces direct output.

Returns if the corresponding expression produces direct output. Direct output is meant that this subexpression produces output such as node constructs or strings.

Return values:

bool true if the corresponding expression produces direct output, false otherwise.

Reimplemented in ForExpression, IfExpression, SequenceExpression, and WhereExpression.

Definition at line 89 of file expression.cpp.

Referenced by IfExpression::containsDirectOutput(), and ForExpression::containsDirectOutput().

void Expression::eval	(	OutputStream &	eos,
		Environment *	env,
		unsigned	modus
	)			`[virtual]`

Evaluates the expression in the given environment.

Evaluates the expression in the given environment. The evaluation takes place in the environment that is passed to this method. In addition, the parameter modus is one of the following: EVAL_QUERY, EVAL_QUERY_SILENT or EVAL_SIGNOFF (see also the corresponding defines for more information). This method implements the XQuery semantics for the standard expression types, but also the GCX specific extensions like signOff-statements.

Parameters:

`[in]`	eos	Pointer to a OutputStream object.
`[in]`	env	Pointer to an Environment object.
`[in]`	modus	The query evaluation mode.

Exceptions:

RuntimeException

If illegal evaluation mode.

Definition at line 86 of file expression.cpp.

Referenced by OrCondExpression::eval(), NotCondExpression::eval(), NodeConstructExpression::eval(), IfExpression::eval(), ForExpression::eval(), AndCondExpression::eval(), Executor::evalQuery(), and ForExpression::evalSignOffForBinding().

void Expression::extractDependencies ( vector< DependencySet * > * depset ) [virtual]

Extracts the needed dependencies of a query.

Extracts the needed dependencies of a query, which are needed for constructing the ProjectionTree.

Parameters:

[in,out] depset Pointer to a vector containing Pointer to DependencySet objects.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ExistsCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, VarExpression, VarstepCondExpression, VarStepExpression, and WhereExpression.

Definition at line 61 of file expression.cpp.

Referenced by Executor::buildDependencies(), OrCondExpression::extractDependencies(), NotCondExpression::extractDependencies(), NodeConstructExpression::extractDependencies(), IfExpression::extractDependencies(), ForExpression::extractDependencies(), CondOperandExpression::extractDependencies(), and AndCondExpression::extractDependencies().

void Expression::extractFSAMap	(	FSAMap *	fsamap,
		unsigned	parent_var
	)			`[virtual]`

Extracts the needed first straight ancestor (FSA) variables map.

Extracts the needed first straight ancestor (FSA) variables map, which is needed for correct insertion of SignOffExpression.

Parameters:

`[in,out]`	fsamap	Pointer to a FSAMap object.
`[in]`	parent_var	Parent variable.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, and WhereExpression.

Definition at line 55 of file expression.cpp.

Referenced by Executor::collectQueryInformation(), OrCondExpression::extractFSAMap(), NotCondExpression::extractFSAMap(), NodeConstructExpression::extractFSAMap(), IfExpression::extractFSAMap(), ForExpression::extractFSAMap(), CondOperandExpression::extractFSAMap(), and AndCondExpression::extractFSAMap().

void Expression::extractParVarMap ( ParVarMap * parvarmap ) [virtual]

Extracts the needed parent variable (ParVar) map.

Extracts the needed parent variable (ParVar) map, which is needed for constructing the VariableTree.

Parameters:

[in,out] parvarmap Pointer to a ParVarMap object.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, and WhereExpression.

Definition at line 58 of file expression.cpp.

Referenced by Executor::collectQueryInformation(), OrCondExpression::extractParVarMap(), NotCondExpression::extractParVarMap(), NodeConstructExpression::extractParVarMap(), IfExpression::extractParVarMap(), ForExpression::extractParVarMap(), CondOperandExpression::extractParVarMap(), and AndCondExpression::extractParVarMap().

const EXP_TYPE Expression::getType ( ) [inline]

Returns the EXP_TYPE of the corresponding expression.

Return values:

EXP_TYPE.

Definition at line 249 of file expression.h.

References type.

Referenced by SequenceExpression::containsDirectOutput(), IfExpression::containsDirectOutput(), ForExpression::containsDirectOutput(), NodeConstructExpression::eval(), SequenceExpression::mergeSequences(), SequenceExpression::print(), OrCondExpression::print(), NodeConstructExpression::print(), ForExpression::print(), AndCondExpression::print(), SequenceExpression::rewriteVarsteps(), NodeConstructExpression::rewriteVarsteps(), IfExpression::rewriteVarsteps(), and ForExpression::rewriteVarsteps().

void Expression::init ( BufferNode * root ) [virtual]

Initializes the query for evaluation.

Initializes the query for evaluation. Up to now only all required BufferIterator objects are created to speed up query evaluation.

Parameters:

[in] root Pointer to a BufferNode object.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ExistsCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, SignOffExpression, VarExpression, VarstepCondExpression, VarStepExpression, and WhereExpression.

Definition at line 83 of file expression.cpp.

Referenced by Executor::evalQuery(), OrCondExpression::init(), NotCondExpression::init(), NodeConstructExpression::init(), IfExpression::init(), ForExpression::init(), CondOperandExpression::init(), and AndCondExpression::init().

void Expression::mergeSequences ( ) [virtual]

Merges belonging together XQuery sequences into a single sequence.

Merges belonging together XQuery sequences into a single sequence, which is done because of better/nicer output look.

Return values:

void

Reimplemented in ForExpression, IfExpression, NodeConstructExpression, SequenceExpression, and WhereExpression.

Definition at line 52 of file expression.cpp.

Referenced by Executor::buildSignOffQuery(), NodeConstructExpression::mergeSequences(), IfExpression::mergeSequences(), ForExpression::mergeSequences(), and Executor::optimizeQuery().

Expression * Expression::placeSignOffs ( vector< SignOffExpression * > & signoffs ) [virtual]

Places all signOff-statements in the corresponding query.

Places all signOff-statements in the corresponding query, which are needed for active garbage collection by removing Role from the BufferNode.

Parameters:

[in] signoffs Pointer to a vector containing Pointer to SignOffExpression objects.

Return values:

Expression*

Pointer to a Expression object (following expression in the corresponding query).

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, and WhereExpression.

Definition at line 64 of file expression.cpp.

Referenced by Executor::insertSignOffs(), OrCondExpression::placeSignOffs(), NotCondExpression::placeSignOffs(), NodeConstructExpression::placeSignOffs(), IfExpression::placeSignOffs(), ForExpression::placeSignOffs(), CondOperandExpression::placeSignOffs(), and AndCondExpression::placeSignOffs().

void Expression::print ( OutputStream & dos ) const [pure virtual]

Prints the expression.

Parameters:

[in] dos Pointer to a OutputStream object.

Return values:

void

Implemented in AggregateFunctExpression, AndCondExpression, CommentExpression, CondOperandExpression, DocExpression, EmptyCondExpression, EmptyExpression, ExistsCondExpression, FalseCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, NumericConstExpression, OrCondExpression, PathExpression, PathStepExpression, PathStepNodeExpression, PathStepStarExpression, PathStepTagExpression, PathStepTextExpression, RoundingExpression, SequenceExpression, SignOffExpression, StringConstExpression, TrueCondExpression, VarExpression, VarstepCondExpression, VarStepExpression, and WhereExpression.

Referenced by operator<<().

void Expression::replaceVarId	(	unsigned	old_id,
		unsigned	new_id
	)			`[virtual]`

Replaces all matching variable IDs by a new one.

Replaces all matching variable IDs by a new one, which is needed in case of calling method rewriteVarsteps().

Parameters:

`[in]`	old_id	Old variable ID.
`[in]`	new_id	New variable ID, which should be introduced instead.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ExistsCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, SignOffExpression, VarExpression, VarstepCondExpression, and WhereExpression.

Definition at line 49 of file expression.cpp.

Referenced by WhereExpression::replaceVarId(), OrCondExpression::replaceVarId(), NotCondExpression::replaceVarId(), NodeConstructExpression::replaceVarId(), IfExpression::replaceVarId(), ForExpression::replaceVarId(), CondOperandExpression::replaceVarId(), AndCondExpression::replaceVarId(), and ForExpression::scopeCheck().

void Expression::rewriteAggregateFuncts ( ) [virtual]

Rewrites all arguments of all aggregate functions into an equivalent for-clause (with return-clause).

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, and WhereExpression.

Definition at line 77 of file expression.cpp.

Referenced by Executor::optimizeQuery(), OrCondExpression::rewriteAggregateFuncts(), NotCondExpression::rewriteAggregateFuncts(), NodeConstructExpression::rewriteAggregateFuncts(), IfExpression::rewriteAggregateFuncts(), ForExpression::rewriteAggregateFuncts(), CondOperandExpression::rewriteAggregateFuncts(), and AndCondExpression::rewriteAggregateFuncts().

void Expression::rewriteEmptyFuncts ( ) [virtual]

Rewrites all fn:empty XQuery functions into equivalent fn:not(fn:exists) XQuery functions.

Return values:

void

Reimplemented in AndCondExpression, CondOperandExpression, EmptyCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, SequenceExpression, and WhereExpression.

Definition at line 71 of file expression.cpp.

Referenced by Executor::optimizeQuery(), OrCondExpression::rewriteEmptyFuncts(), NotCondExpression::rewriteEmptyFuncts(), NodeConstructExpression::rewriteEmptyFuncts(), IfExpression::rewriteEmptyFuncts(), ForExpression::rewriteEmptyFuncts(), CondOperandExpression::rewriteEmptyFuncts(), and AndCondExpression::rewriteEmptyFuncts().

void Expression::rewriteVarstepCondExps ( ) [virtual]

Rewrites all if($x) if-conditions into equivalent if(fn:not(fn:empty($x))) XQuery expressions.

Return values:

void

Reimplemented in AndCondExpression, CondOperandExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, SequenceExpression, VarstepCondExpression, and WhereExpression.

Definition at line 74 of file expression.cpp.

Referenced by Executor::optimizeQuery(), OrCondExpression::rewriteVarstepCondExps(), NotCondExpression::rewriteVarstepCondExps(), NodeConstructExpression::rewriteVarstepCondExps(), IfExpression::rewriteVarstepCondExps(), ForExpression::rewriteVarstepCondExps(), CondOperandExpression::rewriteVarstepCondExps(), and AndCondExpression::rewriteVarstepCondExps().

void Expression::rewriteVarsteps ( ) [virtual]

Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause).

Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause). This method belongs to the 'earlier execution of signoff-statements' optimization.

Return values:

void

Reimplemented in ForExpression, IfExpression, NodeConstructExpression, SequenceExpression, and WhereExpression.

Definition at line 80 of file expression.cpp.

Referenced by Executor::optimizeQuery(), NodeConstructExpression::rewriteVarsteps(), IfExpression::rewriteVarsteps(), and ForExpression::rewriteVarsteps().

void Expression::rewriteWhereExps ( ) [virtual]

Rewrites all where-clauses in the query into equivalent if-expressions.

Rewrites all where-clauses in the query into equivalent if-expressions, i.e. rewrites all WhereExpression into equivalent IfExpression.

Return values:

void

Reimplemented in ForExpression, IfExpression, NodeConstructExpression, SequenceExpression, and WhereExpression.

Definition at line 68 of file expression.cpp.

Referenced by Executor::optimizeQuery(), NodeConstructExpression::rewriteWhereExps(), IfExpression::rewriteWhereExps(), and ForExpression::rewriteWhereExps().

void Expression::scopeCheck	(	vector< unsigned > &	def_vars,
		vector< unsigned > &	introduced_vars,
		vector< unsigned > &	violating_vars
	)			`[virtual]`

Returns if all used variables were previously (through a for-clause) defined or if a variable leaves their defined scope.

Parameters:

`[in]`	def_vars	Vector containing all previously defined variables.
`[in]`	introduced_vars	Vector containing all up to this expression defined variables.
`[in]`	violating_vars	Vector containing all variables which violates the scope condition.

Return values:

void

Reimplemented in AggregateFunctExpression, AndCondExpression, CondOperandExpression, EmptyCondExpression, ExistsCondExpression, ForExpression, IfExpression, NodeConstructExpression, NotCondExpression, OrCondExpression, RoundingExpression, SequenceExpression, SignOffExpression, VarExpression, VarstepCondExpression, and WhereExpression.

Definition at line 44 of file expression.cpp.

Referenced by WhereExpression::scopeCheck(), OrCondExpression::scopeCheck(), NotCondExpression::scopeCheck(), NodeConstructExpression::scopeCheck(), IfExpression::scopeCheck(), ForExpression::scopeCheck(), CondOperandExpression::scopeCheck(), and AndCondExpression::scopeCheck().

void Expression::setType ( EXP_TYPE _type ) [inline]

Sets the EXP_TYPE of the corresponding expression.

Parameters:

[in] _type EXP_TYPE.

Return values:

void

Definition at line 257 of file expression.h.

Referenced by EmptyCondExpression::rewriteEmptyFuncts(), VarstepCondExpression::rewriteVarstepCondExps(), and WhereExpression::rewriteWhereExps().

Member Data Documentation

TagMap * Expression::tagmap [protected]

The map which contains mapping of numeric values of tagnames to their string value.

Definition at line 276 of file expression.h.

Referenced by NodeConstructExpression::eval(), PathStepTagExpression::print(), and NodeConstructExpression::print().

EXP_TYPE Expression::type [protected]

The entered EXP_TYPE.

The entered EXP_TYPE, which is the argument of the constructor.

Definition at line 282 of file expression.h.

Referenced by AggregateFunctExpression::extractDependencies(), PathStepExpression::getNodeTestType(), PathStepExpression::getStepWeight(), getType(), PathStepExpression::isDosNodeStep(), PathStepExpression::isNodeNodeTest(), PathStepExpression::isStarNodeTest(), PathStepExpression::isTagNodeTest(), PathStepExpression::isTextNodeTest(), RoundingExpression::print(), and AggregateFunctExpression::print().


Public Member Functions
	Expression (EXP_TYPE _type)
	Constructor.
virtual	~Expression ()
virtual void	scopeCheck (vector< unsigned > &def_vars, vector< unsigned > &introduced_vars, vector< unsigned > &violating_vars)
	Returns if all used variables were previously (through a for-clause) defined or if a variable leaves their defined scope.
virtual void	replaceVarId (unsigned old_id, unsigned new_id)
	Replaces all matching variable IDs by a new one.
virtual void	mergeSequences ()
	Merges belonging together XQuery sequences into a single sequence.
virtual void	extractFSAMap (FSAMap *fsamap, unsigned parent_var)
	Extracts the needed first straight ancestor (FSA) variables map.
virtual void	extractParVarMap (ParVarMap *parvarmap)
	Extracts the needed parent variable (ParVar) map.
virtual void	extractDependencies (vector< DependencySet * > *depset)
	Extracts the needed dependencies of a query.
virtual Expression *	placeSignOffs (vector< SignOffExpression * > &signoffs)
	Places all signOff-statements in the corresponding query.
virtual void	rewriteWhereExps ()
	Rewrites all where-clauses in the query into equivalent if-expressions.
virtual void	rewriteEmptyFuncts ()
	Rewrites all `fn:empty` XQuery functions into equivalent `fn:not(fn:exists)` XQuery functions.
virtual void	rewriteVarstepCondExps ()
	Rewrites all `if($x)` if-conditions into equivalent `if(fn:not(fn:empty($x)))` XQuery expressions.
virtual void	rewriteAggregateFuncts ()
	Rewrites all arguments of all aggregate functions into an equivalent for-clause (with return-clause).
virtual void	rewriteVarsteps ()
	Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause).
virtual void	print (OutputStream &dos) const =0
	Prints the expression.
virtual void	init (BufferNode *root)
	Initializes the query for evaluation.
virtual void	eval (OutputStream &eos, Environment *env, unsigned modus)
	Evaluates the expression in the given environment.
const EXP_TYPE	getType ()
	Returns the EXP_TYPE of the corresponding expression.
void	setType (EXP_TYPE _type)
	Sets the EXP_TYPE of the corresponding expression.
virtual bool	containsDirectOutput ()
	Returns if the corresponding expression produces direct output.
Protected Attributes
TagMap *	tagmap
EXP_TYPE	type
	The entered EXP_TYPE.